The Lion 10.7.2 update adds the ability to move Spaces and full screen apps.

[crarko adds: When I tried this it looked like Desktop 1 and Dashboard were fixed but I could switch the other Desktops and full screen app Spaces around at will by dragging them in Mission Control. I don't have a 10.7.1 system any more, so I'll trust this is new.]

This is new in the sense that prior to the update you could only move the desktops around in Mission Control if you had *not* selected "Automatically rearrange spaces based on most recent use".

The previous behavior made sense as there should only be one source for determining your spaces ordering, either you or the system frequency. It's not clear what manually reordering spaces does to Lion's most frequently used algorithm.